Fiber blend, spun yarn, textile material, and method for using the textile material

ABSTRACT

The invention provides a fiber blend, spun yarn, and textile material comprising a plurality of cellulosic fibers and a plurality of first synthetic fibers. The first synthetic fibers comprise a polyoxadiazole polymer, and the polyoxadiazole polymer comprises a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below 
     
       
         
         
             
             
         
       
     
     Y is selected from the group consisting of chlorine, bromine, diphenylphosphine oxide, and diphenylphosphine sulfide. The invention also provides a method for protecting an individual from infrared radiation that can be generated during an electrical arc flash using such a textile material.

TECHNICAL FIELD OF THE INVENTION

The invention relates to fiber blends, spun yarns comprising such fiber blends, textile materials comprising the fibers blends and/or spun yarns, and methods for using such textile materials.

BACKGROUND

Flame resistant fabrics are useful in many applications, including the production of garments worn by personnel in a variety of industries or occupations, such as the military, electrical (for arc protection), petroleum chemical manufacturing, and emergency response fields. Cellulosic or cellulosic-blend fabrics have typically been preferred for these garments, due to the relative ease with which these fabrics may be made flame resistant and the relative comfort of such fabrics to the wearer.

Notwithstanding the popularity of cellulosic or cellulosic-blend flame resistant fabrics, existing fabrics do suffer from limitations. The flammability performance of many cellulosic flame resistant fabrics is not sufficient to meet the demanding requirements of certain industries. In order to meet these requirements, inherent flame resistant fibers (e.g., meta-aramid fibers, such as NOMEX® fiber from E. I. du Pont de Nemours and Company) are often employed, which increases the cost of the fabrics. Accordingly, a need remains to provide alternative flame resistant fabrics that are capable of meeting applicable flame resistance standards at lower cost.

BRIEF SUMMARY OF THE INVENTION

In a first embodiment, the invention provides a fiber blend comprising:

(a) a plurality of cellulosic fibers; and

(b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

-   -   wherein Y is selected from the group consisting of chlorine,         bromine, diphenylphosphine oxide, and diphenylphosphine sulfide;         and

wherein the cellulosic fibers and the first synthetic fibers are intimately blended.

In a second embodiment, the invention provides a spun yarn comprising:

(a) a plurality of cellulosic fibers; and

(b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

-   -   wherein Y is selected from the group consisting of chlorine,         bromine, diphenylphosphine oxide, and diphenylphosphine sulfide.

In a third embodiment, the invention provides a textile material comprising:

(a) a plurality of cellulosic fibers; and

(b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

-   -   wherein Y is selected from the group consisting of chlorine,         bromine, diphenylphosphine oxide, and diphenylphosphine sulfide.

In a fourth embodiment, the invention provides a method for protecting an individual from infrared radiation that can be generated during an arc flash, the method comprising the step of positioning a textile material between an individual and an apparatus capable of producing an arc flash, the textile material comprising:

(a) a plurality of cellulosic fibers; and

(b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

-   -   wherein Y is selected from the group consisting of chlorine,         bromine, diphenylphosphine oxide, and diphenylphosphine sulfide.

DETAILED DESCRIPTION OF THE INVENTION

In a first embodiment, the invention provides a fiber blend comprising a plurality of cellulosic fibers and a plurality of first synthetic fibers, the first synthetic fibers comprising a polyoxadiazole polymer. The fibers in the fiber blend preferably are intimately blended so that each different fiber type is substantially evenly distributed throughout the fiber blend.

As noted above, the fiber blend of the invention comprises cellulosic fibers. As utilized herein, the term “cellulosic fibers” is used to refer to fibers composed of, or derived from, cellulose. Examples of suitable cellulosic fibers include cotton, rayon, linen, jute, hemp, cellulose acetate, and combinations, mixtures, or blends thereof. Suitable types of rayon include flame retardant rayon (FR rayon), which is a rayon fiber having a flame retardant compound (e.g., an organophosphorous compound) incorporated therein. FR rayon is available from many sources, such as Lenzing AG. Preferably, the cellulosic fibers comprise cotton fibers. The cotton fibers can, as discussed below, be treated with a phosphorous-containing flame retardant.

In those embodiments comprising cotton fibers, the cotton fibers can be of any suitable variety. Generally, there are two varieties of cotton fibers that are readily available for commercial use in North America: the American Upland variety (Gossypium hirsutum) and the American Pima variety (Gossypium barbadense). The cotton fibers used as the cellulosic fibers in the invention can be cotton fibers of either the American Upland variety, the American Pima variety, or a combination, mixture, or blend of the two. Generally, cotton fibers of the American Upland variety, which comprise the majority of the cotton used in the apparel industry, have lengths ranging from about 0.875 inches to about 1.3 inches, while the less common fibers of the American Pima variety have lengths ranging from about 1.2 inches to about 1.6 inches. Preferably, at least some of the cotton fibers used in the invention are of the American Pima variety, which are preferred due to their greater, more uniform length.

The cellulosic fibers can be present in the fiber blend in any suitable amount. For example, the cellulosic fibers preferably can comprise about 25 wt. % or more, about 30 wt. % or more, about 35 wt. % or more, or about 40 wt. % or more of the fibers present in the fiber blend. The cellulosic fibers preferably can comprise about 90 wt. % or less, about 85 wt. % or less, about 80 wt. % or less, about 75 wt. % or less, about 70 wt. % or less, about 65 wt. % or less, or about 60 wt. % or less of the fibers present in the fiber blend. Thus, in a preferred embodiment, the cellulosic fibers comprise about 25 wt. % to about 90 wt. % (e.g., about 30 wt. % to about 90 wt. %, about 35 wt. % to about 90 wt. %, or about 40 wt. % to about 90 wt. %), about 25 wt. % to about 85 wt. % (e.g., about 30 wt. % to about 85 wt. %, about 35 wt. % to about 85 wt. %, or about 40 wt. % to about 85 wt. %), about 25 wt. % to about 80 wt. % (e.g., about 30 wt. % to about 80 wt. %, about 35 wt. % to about 80 wt. %, or about 40 wt. % to about 80 wt. %), about 25 wt. % to about 75 wt. % (e.g., about 30 wt. % to about 75 wt. %, about 35 wt. % to about 75 wt. %, or about 40 wt. % to about 75 wt. %), about 25 wt. % to about 70 wt. % (e.g., about 30 wt. % to about 70 wt. %, about 35 wt. % to about 70 wt. %, or about 40 wt. % to about 70 wt. %), about 25 wt. % to about 65 wt. % (e.g., about 30 wt. % to about 65 wt. %, about 35 wt. % to about 65 wt. %, or about 40 wt. % to about 65 wt. %), or about 25 wt. % to about 60 wt. % (e.g., about 30 wt. % to about 60 wt. %, about 35 wt. % to about 60 wt. %, or about 40 wt. % to about 60 wt. %) of the fibers present in the fiber blend. In a particularly preferred embodiment, the cellulosic fibers can comprise about 40 wt. % to about 60 wt. % of the fibers present in the fiber blend.

The fiber blend comprises a plurality of first synthetic fibers, and the first synthetic fibers comprise a polyoxadiazole polymer. As will be understood by those of skill in the art, the term “oxadiazole” refers to five-membered, heterocyclic, aromatic groups containing an oxygen atom, two nitrogen atoms, and two carbon atoms, in which at least one of nitrogen atoms is separated from the oxygen atom by a carbon atom. Thus, there are two possible oxadiazole groups: a 1,3,4-oxadiazole group, which has the structure

and a 1,2,4-oxadiazole group, which has the structure

Thus, a polyoxadiazole polymer can comprise a 1,3,4-oxadiazole group, a 1,2,4-oxadiazole group, or a mixture of the two. The polymer in the polyoxadiazole fibers can contain any other suitable repeating group or unit, with arylene groups being particularly preferred. In a preferred embodiment, the first synthetic fibers comprise a polyoxadiazole polymer that comprises a plurality of first repeating units and a plurality of second repeating units. The first repeating units in the polyoxadiazole polymer conform to the structure of Formula (I) below

The second repeating units in the polyoxadiazole polymer conform to the structure of Formula (II) below

In the structure of Formula (II), Y can be any suitable group. Preferably, Y is selected from the group consisting of chlorine, bromine, diphenylphosphine oxide, and diphenylphosphine sulfide. In a particularly preferred embodiment, Y is bromine.

The polyoxadiazole polymer can comprise any suitable amounts (e.g., relative amounts) of the first repeating units and the second repeating units. Generally, the number of the first repeating units in the polyoxadiazole polymer is greater than the number of the second repeating units in the polyoxadiazole polymer. For example, the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer can be about 5:1 or more, about 6:1 or more, about 7:1 or more, about 8:1 or more, or about 9:1 or more. The ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer can be about 25:1 or less, about 24:1 or less, about 23:1 or less, about 22:1 or less, about 21:1 or less, or about 20:1 or less. Thus, in a preferred embodiment, the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is about 5:1 to about 25:1 (e.g., about 6:1 to about 25:1, about 7:1 to about 25:1, about 8:1 to about 25:1, or about 9:1 to about 25:1), about 5:1 to about 24:1 (e.g., about 6:1 to about 24:1, about 7:1 to about 24:1, about 8:1 to about 24:1, or about 9:1 to about 24:1), about 5:1 to about 23:1 (e.g., about 6:1 to about 23:1, about 7:1 to about 23:1, about 8:1 to about 23:1, or about 9:1 to about 23:1), about 5:1 to about 22:1 (e.g., about 6:1 to about 22:1, about 7:1 to about 22:1, about 8:1 to about 22:1, or about 9:1 to about 22:1), about 5:1 to about 21:1 (e.g., about 6:1 to about 21:1, about 7:1 to about 21:1, about 8:1 to about 21:1, or about 9:1 to about 21:1), or about 5:1 to about 20:1 (e.g., about 6:1 to about 20:1, about 7:1 to about 20:1, about 8:1 to about 20:1, or about 9:1 to about 20:1). In one preferred embodiment, the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 5:1 to about 25:1. In another preferred embodiment, the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 9:1 to about 20:1.

While not wishing to be bound to any particular theory, it is believed that the presence of the first synthetic fibers (which comprise a polyoxadiazole polymer as described above) will impart at least some flame resistant properties to the fiber blend and any materials (e.g., spun yarns or fabrics) made therefrom. It is believed that these flame resistant properties are attributable, at least in part, to the relatively high heat stability of the polyoxadiazole polymer. Indeed, it is believed that the particular polyoxadiazole polymer described above (i.e., the polyoxadiazole polymer containing the first repeating units and second repeating units described above) exhibits a more desirable combination of properties (including flame resistance) than other polyoxadiazole polymers (i.e., polyoxadiazole polymers that do not comprise the described combination of repeating units). Thus, as discussed below, it is believed that the fiber blend of the invention and materials made therefrom (e.g., spun yarns and fabrics) are particularly well-suited for use in making flame resistant garments, apparel, and protective equipment.

The first synthetic fibers can be present in the fiber blend in any suitable amount. For example, the first synthetic fibers preferably can comprise about 5 wt. % or more, about 6 wt. % or more, about 7 wt. % or more, about 8 wt. % or more, about 9 wt. % or more, or about 10 wt. % or more of the fiber blend. The first synthetic fibers preferably can comprise about 60 wt. % or less, about 55 wt. % or less, or about 50 wt. % or less of the fiber blend. Thus, in a preferred embodiment, the first synthetic fibers can comprise about 5 wt. % to about 60 wt. % (e.g., about 6 wt. % to about 60 wt. %, about 7 wt. % to about 60 wt. %, about 8 wt. % to about 60 wt. %, about 9 wt. % to about 60 wt. %, or about 10 wt. % to about 60 wt. %), about 5 wt. % to about 55 wt. % (e.g., about 6 wt. % to about 55 wt. %, about 7 wt. % to about 55 wt. %, about 8 wt. % to about 55 wt. %, about 9 wt. % to about 55 wt. %, or about 10 wt. % to about 55 wt. %), or about 5 wt. % to about 50 wt. % (e.g., about 6 wt. % to about 50 wt. %, about 7 wt. % to about 50 wt. %, about 8 wt. % to about 50 wt. %, about 9 wt. % to about 50 wt. %, or about 10 wt. % to about 50 wt. %) of the fiber blend.

The fiber blend can comprise other fibers in addition to the cellulosic fibers and the first synthetic fibers. If present, these additional fibers can be either natural fibers or synthetic fibers. Suitable synthetic fibers include, but are not limited to, antistatic fibers (e.g., electrostatic dissipative fibers), thermoplastic synthetic fibers, and inherent flame resistant fibers. Suitable antistatic or electrostatic dissipative fibers include, but are not limited to, carbon fibers, such as P140 antistatic carbon fibers from DuPont. The antistatic or electrostatic dissipative fibers can be present in the fiber blend in any suitable amount. For example, the antistatic or electrostatic dissipative fibers can comprise about 1 wt. % to about 5 wt. % (e.g., about 1 wt. % to about 3 wt. %, or about 2 wt. %) of the fiber blend. The antistatic fibers have been found to be effective at mitigating electrostatic buildup that can occur in the process of blending the fibers and also imparting antistatic properties to the yarns and textile materials (e.g., fabrics) made from the fiber blend.

Thermoplastic synthetic fibers can be included in the fiber blend to increase the durability of textile materials (e.g., yarns and fabrics) to, for example, industrial washing conditions. In particular, thermoplastic synthetic fibers tend to be rather durable to abrasion and harsh washing conditions employed in industrial laundry facilities and their inclusion in, for example, a spun yarn can increase that yarns durability to such conditions. This increased durability of the yarn, in turn, leads to an increased durability for a textile material made from that yarn. Suitable thermoplastic synthetic fibers include, but are not necessarily limited to, polyester fibers (e.g., poly(ethylene terephthalate) fibers, poly(propylene terephthalate) fibers, poly(trimethylene terephthalate) fibers), poly(butylene terephthalate) fibers, and blends thereof), polyamide fibers (e.g., nylon 6 fibers, nylon 6,6 fibers, nylon 4,6 fibers, and nylon 12 fibers), polyvinyl alcohol fibers, and combinations, mixtures, or blends thereof.

In those embodiments in which the fiber blend comprises thermoplastic synthetic fibers, the thermoplastic synthetic fibers can be present in the fiber blend in any suitable amount. For example, the thermoplastic synthetic fibers can comprise about 1 wt. % or more, about 2 wt. % or more, about 3 wt. % or more, about 4 wt. % or more, or about 5 wt. % or more of the blend. The thermoplastic synthetic fibers can comprise about 50 wt. % or less, about 45 wt. % or less, about 40 wt. % or less, about 35 wt. % or less, about 30 wt. % or less, about 25 wt. % or less, about 20 wt. % or less, or about 15 wt. % or less of the fiber blend. Thus, in a preferred embodiment, the thermoplastic synthetic fibers can comprise about 1 wt. % to about 50 wt. % (e.g., about 1 wt. % to about 45 wt. %, about 1 wt. % to about 40 wt. %, about 1 wt. % to about 35 wt. %, about 1 wt. % to about 30 wt. %, about 1 wt. % to about 25 wt. %, about 1 wt. % to about 20 wt. % or about 1 wt. % to about 15 wt. %), about 2 wt. % to about 50 wt. % (e.g., about 2 wt. % to about 45 wt. %, about 2 wt. % to about 40 wt. %, about 2 wt. % to about 35 wt. %, about 2 wt. % to about 30 wt. %, about 2 wt. % to about 25 wt. %, about 2 wt. % to about 20 wt. % or about 2 wt. % to about 15 wt. %), about 3 wt. % to about 50 wt. % (e.g., about 3 wt. % to about 45 wt. %, about 3 wt. % to about 40 wt. %, about 3 wt. % to about 35 wt. %, about 3 wt. % to about 30 wt. %, about 3 wt. % to about 25 wt. %, about 3 wt. % to about 20 wt. % or about 3 wt. % to about 15 wt. %), about 4 wt. % to about 50 wt. % (e.g., about 4 wt. % to about 45 wt. %, about 4 wt. % to about 40 wt. %, about 4 wt. % to about 35 wt. %, about 4 wt. % to about 30 wt. %, about 4 wt. % to about 25 wt. %, about 4 wt. % to about 20 wt. % or about 4 wt. % to about 15 wt. %), or about 5 wt. % to about 50 wt. % (e.g., about 5 wt. % to about 45 wt. %, about 5 wt. % to about 40 wt. %, about 5 wt. % to about 35 wt. %, about 5 wt. % to about 30 wt. %, about 5 wt. % to about 25 wt. %, about 5 wt. % to about 20 wt. % or about 5 wt. % to about 15 wt. %) of the fiber blend. In one particularly preferred embodiment, the thermoplastic synthetic fibers comprise about 5 wt. % to about 15 wt. % of the fiber blend.

As noted above, the fiber blend can comprise inherent flame resistant fibers in addition to the cellulosic fibers and the first synthetic fibers. As utilized herein, the term “inherent flame resistant fibers” is used to refer to synthetic fibers which, due to the chemical composition of the material from which they are made, exhibit flame resistance without the need for an additional flame retardant treatment. In such embodiments, the inherent flame resistant fibers can be any suitable inherent flame resistant fibers, such as polyoxadiazole fibers (i.e., polyoxadiazole fibers comprising a polyoxadiazole polymer that is different from the polyoxadiazole polymer of the first synthetic fibers), polysulfonamide fibers, poly(benzimidazole) fibers, poly(phenylenesulfide) fibers, meta-aramid fibers, para-aramid fibers, polypyridobisimidazole fibers, polybenzylthiazole fibers, polybenzyloxazole fibers, melamine-formaldehyde polymer fibers, phenol-formaldehyde polymer fibers, oxidized polyacrylonitrile fibers, partially-oxidized polyacrylonitrile fibers, modacrylic fibers, polyamide-imide fibers and combinations, mixtures, or blends thereof. In certain embodiments, the inherent flame resistant fibers are preferably selected from the group consisting of polyoxadiazole fibers, polysulfonamide fibers, poly(benzimidazole) fibers, poly(phenylenesulfide) fibers, meta-aramid fibers, para-aramid fibers, and combinations, mixtures, or blends thereof. In a more specific embodiment, the inherent flame resistant fibers can be selected from the group consisting of polyoxadiazole fibers, polysulfonamide fibers, poly(benzimidazole) fibers, poly(phenylenesulfide) fibers, and combinations, mixtures, or blends thereof.

The inherent flame resistant fibers can be present in the fiber blend in any suitable amount. For example, the inherent flame resistant fibers can comprise about 1 wt. % or more, about 2 wt. % or more, about 3 wt. % or more, about 4 wt. % or more, or about 5 wt. % or more of the fiber blend. The inherent flame resistant fibers can comprise about 40 wt. % or less, about 35 wt. % or less, about 30 wt. % or less, about 25 wt. % or less, about 20 wt. % or less, about 15 wt. % or less, or about 10 wt. % or less of the fiber blend. For example, in one preferred embodiment, the fiber blend can further comprise about 5 wt. % to about 10 wt. % of a para-aramid fiber, which is believed to improve the mechanical strength of the spun yarns and textile materials (e.g., fabrics) made from the fiber blend without compromising (and possibly even improving) the flame resistance of the materials.

The fiber blend of the invention can be used to create a variety of textile materials. For example, the fiber blend can be used alone or in conjunction with other fibers to create nonwoven textile materials. The fiber blend can also be used to produce a spun yarn. Thus, in a second embodiment, the invention provides a spun yarn made from the fiber blend described above. In particular, the invention provides a spun yarn comprising a plurality of cellulosic fibers and a plurality of first synthetic fibers, the first synthetic fibers comprising a polyoxadiazole polymer. Since the spun yarn is made using the fiber blend of the invention, the cellulosic fibers, the first synthetic fibers, and, if present, the additional fibers can be any of those described above in connection with the fiber blend of the invention and such fibers can be present in the spun yarn in any of the amounts described above in connection with the fiber blend of the invention.

The spun yarn of the invention can be made by any suitable spinning process. For example, the spun yarns can be formed by a ring spinning process, an air-jet spinning process, or an open-end spinning process. In certain embodiments, the yarns are spun using a ring spinning process (i.e., the yarns are ring spun yarns).

The fiber blend of the invention and the spun yarn of the invention can each be used to create textile materials. For example, the spun yarn can be used alone or in conjunction with other yarns to produce knit textile materials (e.g., knit fabrics) or woven textile materials (e.g., woven fabrics). Thus, in a third embodiment, the invention provides a textile material comprising a plurality of cellulosic fibers and a plurality of first synthetic fibers, the first synthetic fibers comprising a polyoxadiazole polymer. Since the textile material is made using the fiber blend of the invention or the spun yarn of the invention, the cellulosic fibers, the first synthetic fibers, and, if present, the additional fibers can be any of those described above in connection with the fiber blend of the invention and such fibers can be present in the textile material in any of the amounts described above in connection with the fiber blend of the invention.

As noted above, the textile materials of the invention can be made using the spun yarns of the invention in conjunction with other yarns. In such an embodiment, these additional yarns can be any suitable type of yarn, such as monofilament yarns, multifilament yarns, spun yarns, and combinations of such yarns, and the yarns can comprise any suitable type of fiber, such as natural fibers, synthetic fibers, and combinations of the two. For example, the textile material can be formed using a first plurality of spun yarns according to the invention and a second plurality of spun yarns comprising, for example, cellulosic fibers alone or in combination with thermoplastic synthetic fibers. As explained below, in such an embodiment, the yarns can be disposed in a patternwise arrangement that results in one of the yarns being predominantly disposed on one surface of the textile material and the other yarn being predominantly disposed on the opposite surface of the textile material. With such an arrangement, the textile material can be made in such a way as to place the spun yarns of the invention, which will exhibit flame resistant properties due to the present of the first synthetic fibers, on a surface of the textile material where such flame resistant properties can provide the most benefit when the textile material is worn.

The textile materials of the invention can be of any suitable construction. In other words, the yarns forming the textile material can be provided in any suitable patternwise arrangement producing a fabric. Preferably, the textile materials are provided in a woven construction, such as a plain weave, basket weave, twill weave, satin weave, or sateen weave. Suitable plain weaves include, but are not limited to, ripstop weaves produced by incorporating, at regular intervals, extra yarns or reinforcement yarns in the warp, fill, or both the warp and fill of the textile material during formation. Suitable twill weaves include both warp-faced and fill-faced twill weaves, such as 2/1, 3/1, 3/2, 4/1, 1/2, 1/3, or 1/4 twill weaves. In certain embodiments of the invention, such as when the textile material is formed from two or more pluralities or different types of yarns, the yarns are disposed in a patternwise arrangement in which one of the yarns is predominantly disposed on one surface of the textile material. In other words, one surface of the textile material is predominantly formed by one yarn type. Suitable patternwise arrangements or constructions that provide such a textile material include, but are not limited to, satin weaves, sateen weaves, and twill weaves in which, on a single surface of the fabric, the fill yarn floats and the warp yarn floats are of different lengths.

In one series of embodiments, the invention provides textile materials made from the spun yarns described above, and those textile materials can be flame resistant. As utilized herein, the term “flame resistant” refers to a material that burns slowly or is self-extinguishing after removal of an external source of ignition. The flame resistance of textile materials can be measured by any suitable test method, such as those described in National Fire Protection Association (NFPA) 701 entitled “Standard Methods of Fire Tests for Flame Propagation of Textiles and Films,” ASTM D6413 entitled “Standard Test Method for Flame Resistance of Textiles (vertical test)”, NFPA 2112 entitled “Standard on Flame Resistant Garments for Protection of Industrial Personnel Against Flash Fire”, ASTM F1506 entitled “The Standard Performance Specification for Flame Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazards”, and ASTM F1930 entitled “Standard Test Method for Evaluation of Flame Resistant Clothing for Protection Against Flash Fire Simulations Using an Instrumented Manikin.”

The textile material according to the invention can be treated with one or more flame retardant treatments or finishes to render the textile materials more flame resistant. Typically, such flame retardant treatments or finishes are applied to a textile material containing cellulosic fibers in order to impart flame resistant properties to the cellulosic portion of the textile material. In such embodiments, the flame retardant treatment or finish can be any suitable treatment. Suitable treatments include, but are not limited to, halogenated flame retardants (e.g., brominated or chlorinated flame retardants), phosphorous-based flame retardants, antimony-based flame retardants, nitrogen-containing flame retardants, and combinations, mixtures, or blends thereof.

In one preferred embodiment, the textile material of the invention is treated with a phosphorous-based flame retardant treatment. In this embodiment, a tetrahydroxymethyl phosphonium salt, a condensate of a tetrahydroxymethyl phosphonium salt, or a mixture thereof is first applied to the textile material. As utilized herein, the term “tetrahydroxymethyl phosphonium salt” refers to salts containing the tetrahydroxymethyl phosphonium (THP) cation, which has the structure

including, but not limited to, the chloride, sulfate, acetate, carbonate, borate, and phosphate salts. As utilized herein, the term “condensate of a tetrahydroxymethyl phosphonium salt” (THP condensate) refers to the product obtained by reacting a tetrahydroxymethyl phosphonium salt, such as those described above, with a limited amount of a cross-linking agent, such as urea, guanazole, or biguanide, to produce a compound in which at least some of the individual tetrahydroxymethyl phosphonium cations have been linked through their hydroxymethyl groups. The structure for such a condensate produced using urea is set forth below

The synthesis of such condensates is described, for example, in Frank et al. (Textile Research Journal, November 1982, pages 678-693) and Frank et al. (Textile Research Journal, December 1982, pages 738-750). These THPS condensates are also commercially available, for example, as PYROSAN® CFR from Emerald Performance Materials.

The THP or THP condensate can be applied to the textile material in any suitable amount. Typically, the THP salt or THP condensate is applied to the textile material in an amount that provides at least 0.5% (e.g., at least 1%, at least 1.5%, at least 2%, at least 2.5%, at least 3%, at least 3.5%, at least 4%, or at least 4.5%) of elemental phosphorus based on the weight of the untreated textile material. The THP salt or THP condensate is also typically applied to the textile in an amount that provides less than 5% (e.g., less than 4.5%, less than 4%, less than 3.5%, less than 3%, less than 2.5%, less than 2%, less than 1.5%, or less than 1%) of elemental phosphorus based on the weight of the untreated textile material. Preferably, the THP salt or THP condensate is applied to the textile material in an amount that provides about 1% to about 4% (e.g., about 1% to about 3% or about 1% to about 2%) of elemental phosphorous based on the weight of the untreated textile material.

Once the THP salt or THP condensate has been applied to the textile material, the THP salt or THP condensate is then reacted with a cross-linking agent. The product produced by this reaction is a cross-linked phosphorus-containing flame retardant polymer. The cross-linking agent is any suitable compound that enables the cross-linking and/or curing of THP. Suitable cross-linking agents include, for example, urea, a guanidine (i.e., guanidine, a salt thereof, or a guanidine derivative), guanyl urea, glycoluril, ammonia, an ammonia-formaldehyde adduct, an ammonia-acetaldehyde adduct, an ammonia-butyraldehyde adduct, an ammonia-chloral adduct, glucosamine, a polyamine (e.g., polyethyleneimine, polyvinylamine, polyetherimine, polyethyleneamine, polyacrylamide, chitosan, aminopolysaccharides), glycidyl ethers, isocyanates, blocked isocyanates and combinations thereof. Preferably, the cross-linking agent is urea or ammonia, with urea being the more preferred cross-linking agent.

The cross-linking agent can be applied to the textile material in any suitable amount. The suitable amount of cross-linking agent varies based on the weight of the textile material and its construction. Typically, the cross-linking agent is applied to the textile material in an amount of at least 0.1% (e.g., at least 1%, at least 2%, at least 3%, at least 4%, at least 5%, at least 7%, at least 10%, at least 15%, at least 18%, or at least 20%) based on the weight of the untreated textile material. The cross-linking agent is also typically applied to the textile material in an amount of less than 25% (e.g., less than 20%, less than 18%, less than 15%, less than 12%, less than 10%, less than 7%, less than 5%, less than 3%, or less than 1%) based on the weight of the untreated textile material. In a potentially preferred embodiment, the cross-linking agent is applied to the textile material in an amount of about 4% to about 12% based on the weight of the untreated textile material. In another potentially preferred embodiment, the cross-linking agent is applied to the textile material in an amount of about 2% to about 7% based on the weight of the untreated textile material.

In order to accelerate the condensation reaction of the THP salt or THP condensate and the cross-linking agent, the above-described reaction can be carried out at elevated temperatures. The time and elevated temperatures used in this curing step can be any suitable combinations of times and temperatures that result in the reaction of the THP or THP condensate and cross-linking agent to the desired degree. The time and elevated temperatures used in this curing step can also promote the formation of covalent bonds between the cellulosic fibers and the phosphorous-containing condensation product, which is believed to contribute to the durability of the flame retardant treatment. However, care must be taken not to use excessively high temperatures or excessively long cure times that might result in excessive reaction of the flame retardant with the cellulosic fibers, which might weaken the cellulosic fibers and the textile material. Furthermore, it is believed that the elevated temperatures used in the curing step can allow the THP salt or THP condensate and cross-linking agent to diffuse into the cellulosic fibers where they react to form a cross-linked phosphorus-containing flame retardant polymer within the fibers. Suitable temperatures and times for this curing step will vary depending upon the curing oven used and the speed with which heat is transferred to the textile material, but suitable conditions can range from temperatures of about 149° C. (300° F.) to about 177° C. (350° F.) and times from about 1 minute to about 3 minutes.

In the case where ammonia is used as the cross-linking agent, it is not necessary to use elevated temperatures for the THP salt or THP condensate and cross-linking agent to react. In such case, the reaction can be carried out, for example, in a gas-phase ammonia chamber at ambient temperature. A suitable process for generating a phosphorous-based flame retardant using this ammonia-based process is described, for example, in U.S. Pat. No. 3,900,664 (Miller), the disclosure of which is hereby incorporated by reference.

After the THP salt or THP condensate and cross-linking agent have been cured and allowed to react to the desired degree, the resulting textile material can be exposed to an oxidizing agent. While not wishing to be bound to any particular theory, it is believed that this oxidizing step converts the phosphorous in the condensation product (i.e., the condensation product produced by the reaction of the THP salt or THP condensate and cross-linking agent) from a trivalent form to a more stable pentavalent form. The resulting phosphorous-containing compound (i.e., cross-linked, phosphorous-containing flame retardant polymer) is believed to contain a plurality of pentavalent phosphine oxide groups. In those embodiments in which urea has been used to cross-link the THP salt or THP condensate, the phosphorous-containing compound comprises amide linking groups covalently bonded to the pentavalent phosphine oxide groups, and it is believed that at least a portion of the phosphine oxide groups have three amide linking groups covalently bonded thereto.

The oxidizing agent used in this step can be any suitable oxidant, such as hydrogen peroxide, sodium perborate, or sodium hypochlorite. The amount of oxidant can vary depending on the actual materials used, but typically the oxidizing agent is incorporated in a solution containing at least 0.1% concentration (e.g., at least 0.5%, at least 0.8, at least 1%, at least 2%, or at least 3% concentration) and less than 20% concentration (e.g., less than 15%, less than 12%, less than 10%, less than 3%, less than 2%, or less than 1% concentration) of the oxidant.

After contacting the treated textile material with the oxidizing agent, the cured textile material preferably is contacted with a neutralizing solution (e.g., a caustic solution with a pH of at least 8, at least pH 9, at least pH 10, at least pH 11, or at least pH 12). The actual components of the caustic solution can widely vary, but suitable components include any strong base, such as alkalis. For example, sodium hydroxide (soda), potassium hydroxide (potash), calcium oxide (lime), or any combination thereof can be used in the neutralizing solution. The amount of base depends on the size of the bath and is determined by the ultimately desired pH level. A suitable amount of caustic in the solution is at least 0.1% concentration (e.g., at least 0.5%, at least 0.8%, at least 1%, at least 2%, or at least 3% concentration) and is less than 10% concentration (e.g., less than 8%, less than 6%, less than 5%, less than 3%, less than 2%, or less than 1% concentration). The contact time of the treated textile material with the caustic solution varies, but typically is at least 30 seconds (e.g., at least 1 min, at least 3 min, at least 5 min, or at least 10 min). If desired, the neutralizing solution can be warmed (e.g., up to 75° C., up to 70° C., up to 60° C., up to 50° C., up to 40° C., up to 30° C. relative to room temperature).

In another preferred embodiment, the textile material of the invention is treated with a different phosphorous-containing flame retardant compound. In this embodiment, at least a portion of the textile material is contacted with a treatment composition to deposit the treatment composition thereon. The treatment composition comprises a precondensate compound and a cross-linking composition. The textile material is then heated to a temperature sufficient for the precondensate compound and the cross-linking composition to react in a condensation reaction and produce a phosphorous-containing intermediate polymer. Then, at least a portion of the textile material having the phosphorous-containing intermediate polymer thereon is exposed to an oxidizing agent under conditions sufficient to convert at least a portion of the phosphorous atoms in the phosphorous-containing intermediate polymer to a pentavalent state. The resulting phosphorous-containing polymer exhibits flame resistant properties and imparts those properties to the cellulosic fibers in the textile material.

The treatment composition comprises a precondensate compound and a cross-linking composition. The precondensate compound is produced by the condensation reaction of a reactant mixture comprising a phosphonium compound and a nitrogen-containing compound.

The reactant mixture can comprise any suitable phosphonium compound. As utilized herein, the term “phosphonium compound” refers to a compound containing a phosphonium cation, which is a positively charged substituted phosphine. The phosphonium compound can comprise a phosphonium cation substituted with any suitable substituents, such as alkyl, haloalkyl, alkenyl, and haloalkenyl groups, all of which can be substituted with at least one hydroxyl group. In a preferred embodiment, the reactant mixture comprises at least one phosphonium compound conforming to the structure of Formula (X)

In the structure of Formula (X), R₁ can be any suitable group, such as an alkyl group, a haloalkyl group, an alkenyl group, or a haloalkenyl group. In a preferred embodiment, R₁ is selected from the group consisting of hydrogen, C₁-C₃ alkyl, C₁-C₃ haloalkyl, C₂-C₃ alkenyl, and C₂-C₃ haloalkenyl. In another preferred embodiment, R₁ can be hydrogen. In the structure of Formula (X), X represents an anion and can be any suitable monatomic or polyatomic anion. In a preferred embodiment, X can be an anion selected from the group consisting of halides (e.g., chloride), sulfate, hydrogen sulfate, phosphate, acetate, carbonate, bicarbonate, borate, and hydroxide. In another preferred embodiment, X is a sulfate anion. In the structure of Formula (X), b represents the charge of the anion X. Therefore, in order to provide a phosphonium compound that is charge neutral, the number of phosphonium cations present in the compound is equal to (−b). Examples of phosphonium compounds that are suitable for use in the reactant mixture include, but are not limited to, tetrahydroxymethyl phosphonium salts, such as tetrahydroxymethyl phosphonium chloride, tetrahydroxymethyl phosphonium sulfate, tetrahydroxymethyl phosphonium acetate, tetrahydroxymethyl phosphonium carbonate, tetrahydroxymethyl phosphonium borate, and tetrahydroxymethyl phosphonium phosphate. The reactant mixture can comprise one phosphonium compound, or the reactant mixture can comprise a mixture of two or more phosphonium compounds.

The reactant mixture can comprise any suitable nitrogen-containing compound or combination of nitrogen-containing compounds. In a preferred embodiment, the reactant mixture comprises at least one nitrogen-containing compound conforming to the structure of Formula (XI)

In the structure of Formula (XI), R₂, R₃, R₄, R₅, R₆, and R₇ can be any suitable groups. In a preferred embodiment, R₂, R₃, R₄, R₅, R₆, and R₇ are independently selected from the group consisting of hydrogen, hydroxymethyl, and alkoxymethyl. Suitable nitrogen-containing compounds include, but are not limited to, melamine, methylolated melamines, and alkoxymethyl melamines (e.g., etherified methylol melamines). The reactant mixture can comprise one nitrogen-containing compound, or the reactant mixture can comprise a mixture of two or more nitrogen-containing compounds.

The reactant mixture can contain any suitable amounts of the phosphonium compound and the nitrogen-containing compound. The amounts of the phosphonium compound and the nitrogen-containing compound in the reactant mixture can be expressed through a molar ratio of the two components in the reactant mixture. However, as will be understood by those skilled in the art (and as illustrated below), it is the phosphonium cation(s) in the phosphonium compound that participate in the reaction between the phosphonium compound and the nitrogen-containing compound. (The phosphonium compound's counterion is simply there to balance the charge.) Thus, in order to accurately express the relative amount of each reactive component present in the reactant mixture, the molar amount of the phosphonium compound present in the reactant mixture should be normalized to express the number of reactive phosphonium cations contributed to the reactant mixture by the phosphonium compound. This can be simply done by taking the number of moles of the phosphonium compound present in the reactant mixture and multiplying this value by the number of phosphonium cations present in a molecule of the phosphonium compound. For example, if the reactant mixture contains one mole of a phosphonium compound containing two phosphonium cations per molecule (e.g., tetrahydroxymethyl phosphonium sulfate), then the reactant mixture will contain two moles of reactive phosphonium cations ([1 mole of tetrahydroxymethyl phosphonium sulfate]×[2 phosphonium cations per molecule of tetrahydroxymethyl phosphonium sulfate]=2 moles of phosphonium cations). If two or more phosphonium compounds are present in the reactant mixture, then this calculation must be separately performed for each phosphonium compound. The results from each calculation can then be added to arrive at the total number of moles of reactive phosphonium cations present in the reactant mixture. The FIGURE representing the number of moles of phosphonium cations present in the reactant mixture and the molar amount of the nitrogen-containing compound can then be used to express the relative amounts of the phosphonium compound and the nitrogen-containing compound in the reactant mixture (e.g., a molar ratio of phosphonium cations to nitrogen-containing compound), as discussed below.

Preferably, the phosphonium compound and the nitrogen-containing compound are present in the reactant mixture in an initial molar ratio of phosphonium cations to nitrogen-containing compound of about 50:1 or less, about 40:1 or less, about 30:1 or less, about 25:1 or less, about 20:1 or less, about 15:1 or less, about 10:1 or less, or about 8:1 or less. The phosphonium compound and the nitrogen-containing compound preferably are present in the reactant mixture in an initial molar ratio of phosphonium cations to nitrogen-containing compound of about 3:1 or more or about 6:1 or more. In a preferred embodiment, the phosphonium compound and the nitrogen-containing compound are present in the reactant mixture in an initial molar ratio of phosphonium cations to nitrogen-containing compound of about 50:1 to about 3:1. In another preferred embodiment, the phosphonium compound and the nitrogen-containing compound are present in the reactant mixture in an initial molar ratio of phosphonium cations to nitrogen-containing compound of about 40:1 to about 3:1, about 30:1 to about 3:1, about 25:1 to about 3:1, about 20:1 to about 3:1, about 15:1 to about 3:1 (e.g., about 15:1 to about 6:1), about 10:1 to about 3:1, or about 8:1 to about 3:1 (e.g., about 6:1).

The reactant mixture can contain other components in addition to the phosphonium compound and the nitrogen-containing compound described above. For example, the reactant mixture can contain other nitrogenous compounds, such as urea, guanazole, biguanide, or alkylene ureas. While these other nitrogenous compounds can be present in the reactant mixture, they are typically present in a relatively small amount as compared to the amount of the nitrogen-containing compound present in the reactant mixture. The reactant mixture can also contain a surfactant, such as an alkoxylated alcohol, which aids in the dispersion of the nitrogen-containing compound as described below. The reactant mixture can also contain one or more pH buffers, such as acetate salts (e.g., sodium acetate), phosphate salts (e.g., alkaline metal phosphate salts), tertiary amines, and amino alcohols.

The components of the reactant mixture can be reacted under any suitable conditions which result in a condensation reaction between the phosphonium compound and the nitrogen-containing compound. In one possible embodiment, the phosphonium compound is provided in the form of an aqueous solution and the nitrogen-containing compound (e.g., melamine) is provided in the form of a solid or a solid dispersed in a liquid medium. Generally, in order to facilitate the reaction between the phosphonium compound and the nitrogen-containing compound, the nitrogen-containing compound is provided in the form of a solid (e.g., powder) having relatively small particle size, such as an average particle size of about 100 μm or less. In this embodiment, the nitrogen-containing compound is added to the aqueous solution of the phosphonium compound while the solution is vigorously agitated. In order to further facilitate the incorporation of the nitrogen-containing compound in the solution, a surfactant can be added. Any suitable surfactant can be used, such as an alkoxylated alcohol. Once the nitrogen-containing compound is added to the solution, the resulting reactant mixture is heated to a temperature sufficient to effect a condensation reaction between the phosphonium compound and the nitrogen-containing compound. In a preferred embodiment, the reactant mixture is heated to a temperature of about 60° C. to about 90° C. and maintained within this temperature range for a sufficient amount of time for the phosphonium compound and the nitrogen-containing compound to react, such as about 2 hours to about 8 hours. Generally, the phosphonium compound is provided in a molar excess relative to the amount of the nitrogen-containing compound, and the reactant mixture is maintained at the elevated temperature for a sufficient amount of time for the nitrogen-containing compound to be completely consumed by the condensation reaction. Since the precondensate compound formed by the reaction of the phosphonium compound and the nitrogen-containing compound is water-soluble, the complete consumption of the nitrogen-containing compound can be visually confirmed by the absence of solid particles of the nitrogen-containing compound in the reactant mixture.

Although the exact chemical structure of the precondensate compound has not been determined, the structure of Formula (XII) below depicts one example of a precondensate compound that is believed to be formed by the condensation reaction described above.

The precondensate compound depicted in the structure of Formula (XII) can be produced by reacting a tetrahydroxymethyl phosphonium salt with melamine. For the sake of simplicity, the counterions balancing the overall positive charge of the molecule have not been depicted. As it is depicted in the structure of Formula (XII), the phosphonium compound (i.e., tetrahydroxymethyl phosphonium salt) was present in a sufficient amount to replace each of the six amine hydrogens present on the melamine. With such an excess of the phosphonium compound present in the reactant mixture, the resulting precondensate compound may also contain oligomers (e.g., dimers, trimers, etc.) in which two or more melamine “cores” have been cross-linked by phosphonium compound molecules. Furthermore, when an excess of the phosphonium compound is used, the condensation reaction may produce a precondensate compound that is contained within a composition comprising a significant amount of unreacted phosphonium compound, such as about 1% to about 50% excess phosphonium compound.

In addition to the precondensate compound described above, the treatment composition comprises a cross-linking composition. The cross-linking composition can comprise any suitable cross-linking compound. Preferably, the cross-linking compound comprises two nitrogen-containing functional groups that are capable of reacting with the hydroxyl-bearing carbon atoms of the precondensate compound. (These hydroxyl-bearing carbon atoms are those from the phosphonium compound that did not react with the nitrogen-containing compound when the precondensate compound was formed. An exemplary compound containing such hydroxyl-bearing carbon atoms is depicted in the structure of Formula (XII) above.) Furthermore, each of these reactive nitrogen-containing functional groups preferably has only one hydrogen atom directly bonded to the nitrogen atom. Thus, when such a cross-linking compound reacts with the precondensate compound, the nitrogen-containing functional groups forming the cross-links will no longer have any hydrogen atoms directly bonded to the nitrogen atom of the functional group. While not wishing to be bound to any particular theory, it is believed that such a cross-link (i.e., a cross-link in which the nitrogen atom does not have a hydrogen atom bonded thereto) is less susceptible to oxidative attack (e.g., attack by oxidative chlorine) than a cross-link in which the nitrogen atom still bears a hydrogen atom. This reduced susceptibility to oxidative attack is believed to contribute, at least in part, to the improved wash durability of the flame retardant composition of the invention.

The cross-linking composition can comprise any suitable cross-linking compound possessing the characteristics described above. In a preferred embodiment, the cross-linking composition comprises an alkylene urea compound (e.g., a cyclic alkylene urea compound). In a preferred embodiment, the cross-linking composition comprises an alkylene urea compound selected from the group consisting of ethylene urea, propylene urea, and mixtures thereof.

The cross-linking composition can contain other compounds in addition to the alkylene urea compound mentioned above. For example, the cross-linking composition can contain additional cross-linking agents (i.e., cross-linking agents in addition to the alkylene urea compound). Cross-linking agents suitable for such use include, for example, urea, a guanidine (i.e., guanidine, a salt thereof, or a guanidine derivative, such as cyanoguanidine), guanyl urea, glycoluril, ammonia, an ammonia-formaldehyde adduct, an ammonia-acetaldehyde adduct, an ammonia-butyraldehyde adduct, an ammonia-chloral adduct, glucosamine, a polyamine (e.g., polyethyleneimine, polyvinylamine, polyetherimine, polyethyleneamine, polyacrylamide, chitosan, aminopolysaccharides), glycidyl ethers, isocyanates, blocked isocyanates and combinations thereof. While these other cross-linking agents can be present in the cross-linking composition, they typically are present in a relatively small amount as compared to the amount of the primary cross-linking compound (e.g., alkylene urea) present in the cross-linking composition.

The precondensate compound and the cross-linking composition can be present in the treatment composition in any suitable amounts that permits a condensation reaction between the two. The amounts of the two components in the treatment composition can be expressed in terms of the initial weight ratio of the two components. In a preferred embodiment, the precondensate compound and the cross-linking composition are present in the treatment composition in an initial weight ratio of about 1:2 or more, about 1:1 or more, about 3:2 or more, about 2:1 or more, or about 3:1 or more. In another preferred embodiment, the precondensate compound and the cross-linking composition are present in the treatment composition in an initial weight ratio of precondensate compound to cross-linking composition of about 10:1 or less, about 9:1 or less, about 8:1 or less, about 7:1 or less, about 6:1 or less, about 5:1 or less, about 4:1 or less, or about 3:1 or less. Thus, in certain preferred embodiments, the precondensate compound and the cross-linking composition are present in the treatment composition in an initial weight ratio of precondensate compound to cross-linking composition of about 1:2 to about 10:1 (e.g., about 1:2 to about 5:1), about 1:1 to about 10:1 (e.g., about 1:1 to about 8:1, about 1:1 to about 6:1, about 1:1 to about 5:1, or about 1:1 to about 4:1), about 3:2 to about 10:1 (e.g., about 3:2 to about 8:1, about 3:2 to about 4:1), or about 2:1 to about 10:1 (e.g., about 2:1 to about 8:1, about 2:1 to about 6:1, about 2:1 to about 5:1, about 2:1 to about 4:1, or about 2:1 to about 3:1).

As noted above, the cross-linking composition can contain more than one distinct compound. For the purposes of calculating the ratios described in the preceding paragraph, the amount of the cross-linking composition will be the amount (by weight) of the component(s) in the cross-linking composition that are capable of reacting with the precondensate compound in a condensation reaction. Thus, when the cross-linking composition contains only one compound that is capable of reacting with the precondensate compound (e.g., an alkylene urea), then the amount used in calculating the above-described ratios will be the amount (by weight) of this compound (e.g., the alkylene urea) present in the cross-linking composition. And, if the cross-linking composition contains more than one compound that is capable of reacting with the precondensate compound, the amount used for the purposes of calculating the ratios described in the preceding paragraph will be the total amount (by weight) of “reactive” compounds present in the cross-linking composition. This value is simply the sum of the weight of each “reactive” compound present in the present in the cross-linking composition. In either case, solvents, carriers, and other non-reactive components present in the cross-linking composition are not factored into the calculated ratios described in the preceding paragraph.

The precondensate compound and the cross-linking composition can be provided in any suitable form(s). For example, the precondensate compound can be provided in the form of an aqueous solution, dispersion or suspension. Typically, the precondensate compound is provided in the form of an aqueous solution. In such an embodiment, the cross-linking composition can be provided in the form of a solid that is added to the aqueous solution, or the cross-linking composition can be provided in the form of a solution or dispersion that is mixed with the aqueous solution.

The treatment composition can be applied to the textile material in any suitable amount. One suitable means for expressing the amount of treatment composition that is applied to the textile material is specifying the amount of elemental phosphorous that is added as a percentage of the weight of the untreated textile material (i.e., the textile material prior to the application of the treatment composition described herein). This percentage can be calculated by taking the weight of elemental phosphorous added, dividing this value by the weight of the untreated textile material, and multiplying by 100%. Typically, the treatment composition is applied to the textile material in an amount that provides about 0.5% or more (e.g., about 1% or more, about 1.5% or more, about 2% or more, about 2.5% or more, about 3% or more, about 3.5% or more, about 4% or more, or about 4.5% or more) of elemental phosphorus based on the weight of the untreated textile material. The treatment composition is also typically applied to the textile material in an amount that provides about 5% or less (e.g., about 4.5% or less, about 4% or less, about 3.5% or less, about 3% or less, about 2.5% or less, about 2% or less, about 1.5% or less, or about 1% or less) of elemental phosphorus based on the weight of the untreated textile material. Preferably, the treatment composition is applied to the textile material in an amount that provides about 1% to about 4% (e.g., about 1% to about 3% or about 1% to about 2%) of elemental phosphorous based on the weight of the untreated textile material.

The textile material can be contacted with the treatment composition using any suitable technique, such as any of the wet processing techniques commonly used to treat textile materials. For example, the textile substrate can be contacted with the treatment composition by padding, foaming, or jet “dyeing” (i.e., treating the textile substrate in a jet dyeing machine containing the treatment composition instead of or in addition to a dye liquor).

In order to accelerate the condensation reaction between the precondensate compound and the cross-linking composition, the treated textile material typically is heated to a temperature sufficient for the precondensate compound and the cross-linking composition to react and produce a phosphorous-containing intermediate polymer on the textile material. The time and elevated temperature used in this step can be any suitable combination of time and temperature that results in the reaction of the precondensate compound and cross-linking composition to the desired degree. When the textile material comprises cellulosic fibers, the time and elevated temperatures used in this step can also promote the formation of covalent bonds between the cellulosic fibers and the phosphorous-containing intermediate polymer produced by the condensation reaction, which is believed to contribute to the durability of the flame retardant treatment. However, care must be taken not to use excessively high temperatures or excessively long cure times that might result in excessive reaction of the phosphorous-containing intermediate polymer with the cellulosic fibers, which might weaken the cellulosic fibers and the textile material. Furthermore, it is believed that the elevated temperatures used in the curing step can allow the precondensate compound and cross-linking composition to diffuse into the cellulosic fibers where they then react to form the phosphorus-containing intermediate polymer within the cellulosic fibers. Suitable temperatures and times for this step will vary depending upon the oven used and the speed with which heat is transferred to the textile material, but suitable conditions can range from temperatures of about 149° C. (300° F.) to about 177° C. (350° F.) and times from about 1 minute to about 3 minutes.

The reaction of the precondensate compound and the cross-linking composition results in a phosphorous-containing intermediate polymer. Since the phosphorous-containing intermediate polymer was produced from a precondensate compound containing phosphonium cations, the intermediate polymer will contain quaternary phosphorous atoms. The structure depicted in Formula (XIII) below shows one possible structure for a segment of a polymer produced by the reaction of ethylene urea with a precondensate compound, which precondensate compound has been made by reacting a tetrahydroxymethyl phosphonium salt and melamine.

While such a polymer (i.e., a polymer containing quaternary phosphorous atoms) is relatively stable, it is believed that the stability and, for example, wash durability of the polymer can be increased by converting at least a portion of the phosphorous atoms in the polymer into a pentavalent state. The structure depicted in Formula (XIV) below shows the segment depicted in Formula (XIII) after the phosphorous atoms have been converted into a pentavalent state.

As can be seen from the structure depicted above, the conversion of a phosphorous atom from a quaternary state to a pentavalent involves an oxidation that converts the quaternary phosphonium group into a phosphine oxide group. This conversion (i.e., oxidation of the quaternary phosphonium groups to a pentavalent state) can be effected by reacting the phosphorous-containing intermediate polymer with a suitable oxidizing agent. Suitable oxidizing agents include, but are not limited to, oxygen (e.g., gaseous oxygen), hydrogen peroxide, sodium perborate, sodium hypochlorite, percarbonate (e.g., alkaline metal percarbonates), ozone, peracetic acid, and mixtures or combinations thereof. Suitable oxidizing agents also include compounds that are capable of generating hydrogen peroxide or peroxide species, which compounds can be used alone or in combination with any of the oxidizing agents listed above. As noted above, the phosphorous containing intermediate polymer is exposed to the oxidizing agent for a period of time and under conditions sufficient for at least a portion of the phosphorous atoms in the intermediate polymer to be converted to a pentavalent state. In a preferred embodiment, the phosphorous containing intermediate polymer is exposed to the oxidizing agent for a period of time and under conditions sufficient to convert substantially all of the phosphorous atoms in the intermediate polymer to a pentavalent state.

After the treatment composition has been applied to the textile material and the components of the treatment composition have been allowed to react in the above-described condensation reaction, the resulting textile material can be exposed to an oxidizing agent in order to convert at least a portion of the phosphorous atoms in the phosphorous-containing intermediate polymer into a pentavalent state. The mechanism of and reasons for this conversion have been described above. Furthermore, oxidizing agents suitable for use in this step have also been described above, and each of these oxidizing agents (or any suitable combination thereof) can be used in this step of treating the textile material.

The textile material can be exposed to the oxidizing agent using any suitable technique. For example, the textile material can be exposed to the oxidizing agent using any of the wet processing techniques commonly used to treat textile materials, such as those described above in connection with the application of the treatment composition to the textile material. The amount of oxidizing agent used in treating the textile material can vary depending on the actual materials used, but typically the oxidizing agent is incorporated in a solution containing about 0.1% or more (e.g., about 0.5% or more, about 0.8% or more, about 1% or more, about 2% or more, or about 3% or more) and about 20% or less (e.g., about 15% or less, about 12% or less, about 10% or less, about 3% or less, about 2% or less, or about 1% or less), by weight, of the oxidizing agent.

After contacting the textile material with the oxidizing agent, the treated textile material can be contacted with a neutralizing solution (e.g., a caustic solution with a pH of about 8 or more, about 9 or more, about 10 or more, about 11 or more, or about 12 or more). The actual components of the caustic solution can widely vary, but suitable components include any strong base, such as alkalis. For example, sodium hydroxide (soda), potassium hydroxide (potash), calcium oxide (lime), or any combination thereof can be used in the neutralizing solution. The amount of base depends on the size of the bath and is determined by the ultimately desired pH level. A suitable amount of caustic in the solution is about 0.1% or more (e.g., about 0.5% or more, about 0.8% or more, about 1% or more, about 2% or more, or about 3% or more) and is about 10% or less (e.g., about 8% or less, about 6% or less, about 5% or less, about 3% or less, about 2% or less, or about 1% or less). The contact time of the treated textile material with the caustic solution varies, but typically is about 30 seconds or more (e.g., about 1 min or more, about 3 min or more, about 5 min or more, or about 10 min or more). If desired, the neutralizing solution can be warmed (e.g., up to about 75° C. greater, up to about 70° C. greater, up to about 60° C. greater, up to about 50° C. greater, up to about 40° C. greater, or up to about 30° C. greater than the ambient temperature).

After the treated textile material has been contacted with the oxidizing agent as described above and, if desired, contacted with a neutralizing solution as described above, the treated textile material typically is rinsed to remove any unreacted components from the treatment composition, any residual oxidizing agent, and (if the neutralization step was performed) any residual components from the neutralizing solution. The treated textile material can be rinsed in any suitable medium, provided the medium does not degrade the phosphorous-containing polymer. Typically, the treated textile material is rinsed in water (e.g., running water) until the pH of the water is relatively neutral, such as a pH of about 6 to about 8, or about 7. After rinsing, the treated textile material is dried using suitable textile drying conditions.

If desired, the textile material can be treated with one or more softening agents (also known as “softeners”) to improve the hand of the treated textile material. The softening agent selected for this purpose should not have a deleterious effect on the flammability of the resultant fabric. Suitable softeners include polyolefins, alkoxylated alcohols (e.g., ethoxylated alcohols), alkoxylated ester oils (e.g., ethoxylated ester oils), alkoxylated fatty amines (e.g., ethoxylated tallow amine), alkyl glycerides, alkylamines, quaternary alkylamines, halogenated waxes, halogenated esters, silicone compounds, and mixtures thereof. In a preferred embodiment, the softener is selected from the group consisting of cationic softeners and nonionic softeners.

The softener can be present in the textile material in any suitable amount. One suitable means for expressing the amount of treatment composition that is applied to the textile material is specifying the amount of softener that is applied to the textile material as a percentage of the weight of the untreated textile material (i.e., the textile material prior to the application of the treatment composition described herein). This percentage can be calculated by taking the weight of softener solids applied, dividing this value by the weight of the untreated textile material, and multiplying by 100%. Preferably, the softener is present in the textile material in an amount of about 0.1% or more, about 0.2% or more, or about 0.3% or more, by weight, based on the weight of the untreated textile material. Preferably, the softener is present in the textile material in an amount of about 10% or less, about 9% or less, about 8% or less, about 7% or less, about 6% or less, or about 5% or less, by weight, based on the weight of the untreated textile material. Thus, in certain preferred embodiments, the softener is present in the textile material in an amount of about 0.1% to about 10%, about 0.2% to about 9% (e.g., about 0.2% to about 8%, about 0.2% to about 7%, about 0.2% to about 6%, or about 0.2% to about 5%), or about 0.3% to about 8% (e.g., about 0.3% to about 7%, about 0.3% to about 6%, or about 0.3% to about 5%), by weight, based on the weight of the untreated textile material.

To further enhance the textile material's hand, the textile material can optionally be treated using one or more mechanical surface treatments. A mechanical surface treatment typically relaxes stress imparted to the fabric during curing and fabric handling, breaks up yarn bundles stiffened during curing, and increases the tear strength of the treated fabric. Examples of suitable mechanical surface treatments include treatment with high-pressure streams of air or water (such as those described in U.S. Pat. No. 4,918,795, U.S. Pat. No. 5,033,143, and U.S. Pat. No. 6,546,605), treatment with steam jets, needling, particle bombardment, ice-blasting, tumbling, stone-washing, constricting through a jet orifice, and treatment with mechanical vibration, sharp bending, shear, or compression. A sanforizing process may be used instead of, or in addition to, one or more of the above processes to improve the fabric's hand and to control the fabric's shrinkage. Additional mechanical treatments that may be used to impart softness to the treated fabric, and which may also be followed by a sanforizing process, include napping, napping with diamond-coated napping wire, gritless sanding, patterned sanding against an embossed surface, shot-peening, sand-blasting, brushing, impregnated brush rolls, ultrasonic agitation, sueding, engraved or patterned roll abrasion, and impacting against or with another material, such as the same or a different fabric, abrasive substrates, steel wool, diamond grit rolls, tungsten carbide rolls, etched or scarred rolls, or sandpaper rolls.

The textile material of the invention can be used alone or in conjunction with other textile materials to produce garments and other forms of protective apparel (e.g., vests, aprons, hoods, gloves, and chaps). Given the flame resistant properties imparted to the textile material by the inclusion of the first synthetic fibers, it is believed that the textile material of the invention is particularly well-suited for use in producing apparel that is used to protect the wearer from injury caused by exposure to fire or intense infrared radiation.

In a fourth embodiment, the invention provides a method for protecting an individual from infrared radiation that can be generated during an electrical arc flash. In this embodiment, the method comprises the step of positioning a textile material between an individual and an apparatus capable of producing an electrical arc flash. The textile material preferably is a textile material according to the invention, such as any embodiment of the textile material described above.

In this method embodiment of the invention, the textile material can be positioned at any suitable point between the individual and the apparatus. However, in order to ensure that the textile material is positioned to afford the greatest degree of protection to the individual, the textile material preferably forms part of a garment worn by the individual. Suitable garments include, but are not limited to, shirts, pants, coats, hoods, aprons, and gloves. In a preferred embodiment, the outward-facing textile portions of a garment worn by the individual (i.e., those portions of the garment facing towards the apparatus when the garment is being worn by the individual) consist essentially of (or even more preferably consist of) a textile material according to the invention.

The method described above can be used to protect an individual from an arc flash produced by any apparatus. Typically, the apparatus is a piece of electrical equipment. Preferably, the apparatus is capable of producing an arc flash having an incident energy of about 1.2 calories/cm² or more (about 5 J/cm² or more) at a position at which the individual is located. More preferably, the apparatus is capable of producing an arc flash having an incident energy of about 4 calories/cm² or more (about 17 J/cm² or more) at a position at which the individual is located. The apparatus preferably is capable of producing an arc flash having an incident energy of about 8 calories/cm² or more (about 33 J/cm² or more) at a position at which the individual is located. An arc flash having an incident energy such as those described above (especially an arc flash having an incident energy of about 4 calories/cm² or more or about 8 calories/cm² or more) is capable of inflicting significant injury (e.g., second degree burns) to the unprotected or under-protected skin of an individual exposed to the arc flash.

The materials of the invention (e.g., fiber blend, spun yarn, textile material of the invention) can be dyed to impart a desired shade to the material. The materials of the invention can be dyed using any suitable colorant or combination of colorants, such as pigments, dyes, and combinations thereof. For example, the first synthetic fibers can be dyed using cationic (basic) dyes. Applicants have found that vat dyes are particularly useful in dyeing the materials of the invention. While not wishing to be bound to any particular theory, it is believed that vat dyes are particularly useful because the vat dyes are capable of dyeing both the cellulosic fibers and the first synthetic fibers, which comprise the polyoxadiazole polymer. This is surprising because vat dyes typically are not used to dye synthetic fibers. While the vat dyes can be used and will result in dyeing of both the cellulosic fibers and the first synthetic fibers, the first synthetic fibers require a higher-than-expected amount of the vat dye(s) in order to produce the desired shade (i.e., the amount of vat dye(s) required to dye the first synthetic fibers a desired shade is greater than the amount required to dye a similar amount of a different fiber [e.g., cotton fiber] the same desired shade). In fact, Applicants have found that the amount of vat dye(s) needed to dye a given amount of the first synthetic fibers typically is about twice the amount needed to dye the same amount of cotton fibers. Thus, when a material (e.g., fiber blend, spun yarn, or textile material) of the invention is dyed using a vat dye, the amount of vat dye(s) used should be increased accordingly, which increased amount will depend upon the amount of the first synthetic fibers present in the material. Applicants have also found that, by dyeing the material with vat dyes, the resulting color exhibits improved colorfastness to light exposure, and the material is stabilized against degradation by ultraviolet light. As noted above, the materials of the invention can be dyed with other dyes, such as disperse dyes. Typically, these dyes are used in combination with vat dyes when the material contains other synthetic fibers, such as thermoplastic synthetic fibers (e.g., polyester fibers or polyamide fibers).

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the subject matter of this application (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the subject matter of the application and does not pose a limitation on the scope of the subject matter unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the subject matter described herein.

Preferred embodiments of the subject matter of this application are described herein, including the best mode known to the inventors for carrying out the claimed subject matter. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the subject matter described herein to be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the present disclosure unless otherwise indicated herein or otherwise clearly contradicted by context. 

What is claimed is:
 1. A fiber blend comprising: (a) a plurality of cellulosic fibers; and (b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

wherein Y is selected from the group consisting of chlorine, bromine, diphenylphosphine oxide, and diphenylphosphine sulfide; wherein the cellulosic fibers and the first synthetic fibers are intimately blended.
 2. The fiber blend of claim 1, wherein the cellulosic fibers comprise about 40 wt. % to about 80 wt. % of the fiber blend.
 3. The fiber blend of claim 1, wherein Y is bromine.
 4. The fiber blend of claim 1, wherein the first synthetic fibers comprise about 10 wt. % to about 50 wt. % of the fiber blend.
 5. The fiber blend of claim 1, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 5:1 to about 25:1.
 6. The fiber blend of claim 5, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 9:1 to about 20:1.
 7. The fiber blend of claim 1, wherein the fiber blend comprises about 5 wt. % to about 15 wt. % of a plurality of second synthetic fibers.
 8. The fiber blend of claim 7, wherein the second synthetic fibers are selected from the group consisting of antistatic fibers, polyamide fibers, polyester fibers, and blends thereof.
 9. The fiber blend of claim 1, wherein the fiber blend further comprises a phosphorous-containing flame retardant.
 10. A spun yarn comprising: (a) a plurality of cellulosic fibers; and (b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

wherein Y is selected from the group consisting of chlorine, bromine, diphenylphosphine oxide, and diphenylphosphine sulfide.
 11. The spun yarn of claim 10, wherein the cellulosic fibers comprise about 40 wt. % to about 80 wt. % of the spun yarn.
 12. The spun yarn of claim 10, wherein Y is bromine.
 13. The spun yarn of claim 10, wherein the first synthetic fibers comprise about 10 wt. % to about 50 wt. % of the spun yarn.
 14. The spun yarn of claim 10, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 5:1 to about 25:1.
 15. The spun yarn of claim 14, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 9:1 to about 20:1.
 16. The spun yarn of claim 10, wherein the spun yarn comprises about 5 wt. % to about 15 wt. % of a plurality of second synthetic fibers.
 17. The spun yarn of claim 16, wherein the second synthetic fibers are selected from the group consisting of antistatic fibers, polyamide fibers, polyester fibers, and blends thereof.
 18. The spun yarn of claim 10, wherein the spun yarn further comprises a phosphorous-containing flame retardant.
 19. The spun yarn of claim 10, wherein the spun yarn further comprises a vat dye, and the vat dye is deposited on both the cellulosic fibers and the first synthetic fibers.
 20. A textile material comprising: (a) a plurality of cellulosic fibers; and (b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

wherein Y is selected from the group consisting of chlorine, bromine, diphenylphosphine oxide, and diphenylphosphine sulfide.
 21. The textile material of claim 20, wherein the cellulosic fibers comprise about 40 wt. % to about 80 wt. % of the textile material.
 22. The textile material of claim 20, wherein Y is bromine.
 23. The textile material of claim 20, wherein the first synthetic fibers comprise about 10 wt. % to about 50 wt. % of the textile material.
 24. The textile material of claim 20, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 5:1 to about 25:1.
 25. The textile material of claim 24, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 9:1 to about 20:1.
 26. The textile material of claim 20, wherein the textile material comprises about 5 wt. % to about 15 wt. % of a plurality of second synthetic fibers.
 27. The textile material of claim 26, wherein the second synthetic fibers are selected from the group consisting of antistatic fibers, polyamide fibers, polyester fibers, and blends thereof.
 28. The textile material of claim 20, wherein the textile material further comprises a phosphorous-containing flame retardant.
 29. The textile material of claim 20, wherein the textile material further comprises a vat dye, and the vat dye is deposited on both the cellulosic fibers and the first synthetic fibers.
 30. A method for protecting an individual from infrared radiation that can be generated during an arc flash, the method comprising the step of positioning a textile material between an individual and an apparatus capable of producing an arc flash, the textile material comprising: (a) a plurality of cellulosic fibers; and (b) a plurality of first synthetic fibers comprising a polyoxadiazole polymer, the polyoxadiazole polymer comprising a plurality of first repeating units and a plurality of second repeating units, the first repeating units conforming to the structure of Formula (I) below and the second repeating units conforming to the structure of Formula (II) below

wherein Y is selected from the group consisting of chlorine, bromine, diphenylphosphine oxide, and diphenylphosphine sulfide.
 31. The method of claim 30, wherein the textile material is part of a garment worn by the individual.
 32. The method of claim 30, wherein the cellulosic fibers comprise about 40 wt. % to about 80 wt. % of the textile material.
 33. The method of claim 30, wherein Y is bromine.
 34. The method of claim 30, wherein the first synthetic fibers comprise about 10 wt. % to about 50 wt. % of the textile material.
 35. The method of claim 30, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 5:1 to about 25:1.
 36. The method of claim 35, wherein the ratio of the number of first repeating units in the polyoxadiazole polymer to the number of second repeating units in the polyoxadiazole polymer is from about 9:1 to about 20:1.
 37. The method of claim 30, wherein the textile material comprises about 5 wt. % to about 15 wt. % of a plurality of second synthetic fibers.
 38. The method of claim 37, wherein the second synthetic fibers are selected from the group consisting of antistatic fibers, polyamide fibers, polyester fibers, and blends thereof.
 39. The method of claim 30, wherein the textile material further comprises a phosphorous-containing flame retardant.
 40. The method of claim 20, wherein the textile material further comprises a vat dye, and the vat dye is deposited on both the cellulosic fibers and the first synthetic fibers. 